org.locationtech.proj4j.proj.RobinsonProjection Maven / Gradle / Ivy

/*******************************************************************************
 * Copyright 2006, 2017 Jerry Huxtable, Martin Davis
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * This file was semi-automatically converted from the public-domain USGS PROJ source.
 */
package org.locationtech.proj4j.proj;

import org.locationtech.proj4j.ProjCoordinate;
import org.locationtech.proj4j.ProjectionException;
import org.locationtech.proj4j.util.ProjectionMath;

public class RobinsonProjection extends PseudoCylindricalProjection {

	private final static double X[] = {
		1,	-5.67239e-12,	-7.15511e-05,	3.11028e-06,
		0.9986,	-0.000482241,	-2.4897e-05,	-1.33094e-06,
		0.9954,	-0.000831031,	-4.4861e-05,	-9.86588e-07,
		0.99,	-0.00135363,	-5.96598e-05,	3.67749e-06,
		0.9822,	-0.00167442,	-4.4975e-06,	-5.72394e-06,
		0.973,	-0.00214869,	-9.03565e-05,	1.88767e-08,
		0.96,	-0.00305084,	-9.00732e-05,	1.64869e-06,
		0.9427,	-0.00382792,	-6.53428e-05,	-2.61493e-06,
		0.9216,	-0.00467747,	-0.000104566,	4.8122e-06,
		0.8962,	-0.00536222,	-3.23834e-05,	-5.43445e-06,
		0.8679,	-0.00609364,	-0.0001139,	3.32521e-06,
		0.835,	-0.00698325,	-6.40219e-05,	9.34582e-07,
		0.7986,	-0.00755337,	-5.00038e-05,	9.35532e-07,
		0.7597,	-0.00798325,	-3.59716e-05,	-2.27604e-06,
		0.7186,	-0.00851366,	-7.0112e-05,	-8.63072e-06,
		0.6732,	-0.00986209,	-0.000199572,	1.91978e-05,
		0.6213,	-0.010418,	8.83948e-05,	6.24031e-06,
		0.5722,	-0.00906601,	0.000181999,	6.24033e-06,
		0.5322, 0., 0., 0.
	};

	private final static double Y[] = {
		0,	0.0124,	3.72529e-10,	1.15484e-09,
		0.062,	0.0124001,	1.76951e-08,	-5.92321e-09,
		0.124,	0.0123998,	-7.09668e-08,	2.25753e-08,
		0.186,	0.0124008,	2.66917e-07,	-8.44523e-08,
		0.248,	0.0123971,	-9.99682e-07,	3.15569e-07,
		0.31,	0.0124108,	3.73349e-06,	-1.1779e-06,
		0.372,	0.0123598,	-1.3935e-05,	4.39588e-06,
		0.434,	0.0125501,	5.20034e-05,	-1.00051e-05,
		0.4958,	0.0123198,	-9.80735e-05,	9.22397e-06,
		0.5571,	0.0120308,	4.02857e-05,	-5.2901e-06,
		0.6176,	0.0120369,	-3.90662e-05,	7.36117e-07,
		0.6769,	0.0117015,	-2.80246e-05,	-8.54283e-07,
		0.7346,	0.0113572,	-4.08389e-05,	-5.18524e-07,
		0.7903,	0.0109099,	-4.86169e-05,	-1.0718e-06,
		0.8435,	0.0103433,	-6.46934e-05,	5.36384e-09,
		0.8936,	0.00969679,	-6.46129e-05,	-8.54894e-06,
		0.9394,	0.00840949,	-0.000192847,	-4.21023e-06,
		0.9761,	0.00616525,	-0.000256001,	-4.21021e-06,
		1., 0., 0., 0
	};

	private final int NODES = 18;
	private final static double FXC = 0.8487;
	private final static double FYC = 1.3523;
	private final static double C1 = 11.45915590261646417544;
	private final static double RC1 = 0.08726646259971647884;
	private final static double ONEEPS = 1.000001;
	private final static double EPS = 1e-8;
	
	public RobinsonProjection() {
	}

	private double poly(double[] array, int offset, double z) {
		return (array[offset] + z * (array[offset+1] + z * (array[offset+2] + z * array[offset+3])));
	}

	public ProjCoordinate project(double lplam, double lpphi, ProjCoordinate xy) {
		double phi = Math.abs(lpphi);
		int i = (int)Math.floor(phi * C1);
		if (i >= NODES)
			i = NODES - 1;
		phi = Math.toDegrees(phi - RC1 * i);
		i *= 4;
		xy.x = poly(X, i, phi) * FXC * lplam;
		xy.y = poly(Y, i, phi) * FYC;
		if (lpphi < 0.0)
			xy.y = -xy.y;
		return xy;
	}

	public ProjCoordinate projectInverse(double x, double y, ProjCoordinate lp) {
		int i;
		double t, t1;

		lp.x = x / FXC;
		lp.y = Math.abs(y / FYC);
		if (lp.y >= 1.0) {
			if (lp.y > 1.000001) {
				throw new ProjectionException();
			} else {
				lp.y = y < 0. ? -ProjectionMath.HALFPI : ProjectionMath.HALFPI;
				lp.x /= X[4*NODES];
			}
		} else {
			for (i = 4 * (int)Math.floor(lp.y * NODES);;) {
				if (Y[i] > lp.y)
					i -= 4;
				else if (Y[i+4] <= lp.y)
					i += 4;
				else
					break;
			}
			t = 5. * (lp.y - Y[i])/(Y[i+4] - Y[i]);
			double Tc0 = Y[i];
			double Tc1 = Y[i+1];
			double Tc2 = Y[i+2];
			double Tc3 = Y[i+3];
			t = 5. * (lp.y - Tc0)/(Y[i+1] - Tc0);
			Tc0 -= lp.y;
			for (;;) { // Newton-Raphson
				t -= t1 = (Tc0 + t * (Tc1 + t * (Tc2 + t * Tc3))) / (Tc1 + t * (Tc2 + Tc2 + t * 3. * Tc3));
				if (Math.abs(t1) < EPS)
					break;
			}
			lp.y = Math.toRadians(5 * i + t);
			if (y < 0.)
				lp.y = -lp.y;
			lp.x /= poly(X, i, t);
		}
		return lp;
	}

	public boolean hasInverse() {
		return true;
	}

	public String toString() {
		return "Robinson";
	}

}